Currently, 2D projection X-Ray or X-Ray computed tomography (CT) are frequently used as imaging modalities for bone imaging. However, ionizing radiation exposure to patients and caregivers from such medical imaging has increased dramatically in past decades (estimated at 600% increase since the 1980's). The cumulative effect of such radiation dosages has been linked to increased risk of cancer.
U.S. Pat. No. 6,641,537 (Morris et al.) mentions taking quantitative measurements of bone in vivo using ultrasound. U.S. Pat. No. 6,964,639 (Sela et al.) mentions mapping irregularities of bone using ultrasound. U.S. Pat. No. 6,106,464 (Bass et al.) mentions image-guided surgery in the brain. U.S. Pat. No. 7,806,823 (Sakai et al.) mentions an imaging technique for mechanical testing of bone.